The ACL stabilises the knee for reducing, twisting and jumping and pivoting exercise. The anterior cruciate ligament is in the middle of the knee joint. When you tear an ACL, you may usually sense or listen to a pop, sense the knee shift outside of spot and create sizeable swelling https://www.theorthopaedicandpainpractice.com/what-should-i-do-if-i-have-a-collateral-ligament-injury-of-the-knee/?_gl=1*xbbxlb*_up*MQ..&gclid=Cj0KCQjwkt6aBhDKARIsAAyeLJ2krYJSOuy5mZksrNqH-VDjQwW1ScD49yD8BUWysDG6u6bJPCSbXVUaAuCPEALw_wcB